Process of unhairing hides or skins



Patented Dec. 16, 1930 warren STATES PATENT OFFICE GEORGE DUNLAPMOLAUGHLIN, GEORGE EDMUND ROCKWELL, FREDERICK OI'ILA HERTY, AND JOHNHENRY HIGHBERGER, OF CINCINNATI, OHIO, ASSIGNORS TO TANNERS COUNCIL OFTHE UNITED STATES OF AMERICA, OF NEW YORK, N. Y.,

' A CORPORATION OF THE DISTRICT OF COLUMBIA PROCESS OF UNHAIRING HIDESOR SKINS No Drawing.

complete the process of unhairing hides or skins during a lesser periodof time than heretofore necessary and yet accomplishthe completion ofthe' unhairing process without creating or leavin any deleterious effectupon the hides or s ins or upon the removed hair.

Another object resides in devising a rocess for unhairing andcondltiomngs h1 es or skins which will create an economic saving 111 themanufacture of leather.

fi l

Other objects will be pointed out hereinafter in the description andclaims.

Various processes are employed b manufacturers of leather for bringing aout the removal of hair or-wool from animal skins prior to tannin and,in general, when the skin is received liy the tanner it is soaked inWater or a dilute solution of some chemical; this process istermedsoaking. Soaking results in hydrating the skin and thus bringing it intoa soft, liable condition and partially swelling or distendini it.Soaking also serves to remove most of e curing salt the skin contains(in the case of salted skins), to remove certain undesirable protein andprotein-like bodies the skin contains, and to remove adhering blood;dirt'and foreign substances. After prbperly soaking, the skin is placedin the unhairing solution. The unhairingsolutions at present employedvary in composition. The solution most widely used is a saturatedsolution of calcium hydroxide containing excess undissolved calciumhydroxide so that the solution will remain sat- =rurated (or nearly so)with calcium hydroxide at all time's, the calcium hydroxide absorbed bythe skins-and thus removed from the Among the objects of our inventionis to.

Application filed March 15, 1927. Serial No. 175,627.

solutionbeing automatically replaced in the solution by the excess,undissolved calcium hydroxide present. For the purpose of hastening theaction of the solution upon the skin, sulphides of sodium or of arsenicare often added to calcium hydroxide solution. Solutions of otheralkalies, notably sodium hydroxide, are sometimes used in place ofcalcium hydroxide or may be added to itfi In some cases the alkalinesolutions described are substituted for by a mixture of sodium sulphideand calcium hydroxide, which mixture has theconsistency of a paste andis painted or spread over the fleshside (opposite the hair side) of askin and allowed to remain until the'mixture has penetrated through theskin and so acted upon the skin and upon the hair or wool that thelatter may be easily removed by mechanical means. There are otherprocesses of unhairing, for example, that process known as sweating,whereby skins are placed in a warm, humid room until the bacteria of theskin bring about its partial decomposition and consequent loosening ofits halr. Another process consists in the treatment of the skin withcertain enzymes, usually in conjunction with I the action of alkalies.

- Whichever of the known unhairin processes is used, the time requiredfor t e unhairin operation and the manipulation of the un airingagencies, varies with the condition of the skin and the character ofleather to be produced. In all cases, however, it is the aim and desireof the tanner to bring about proper unhairing and pro er skin conditionas rapidly as possible. 11 achieving these results it is to the interestof the tanner that the amount of needed equipment he minimized, thelabor cost of handling be lowered, the interest charges on moneyinvested in skins be reduced and the total time required for manufacturebe shortened.

. and the hair (a valuable by-product) is often until the skins hair maybe readily removed.

adversely affected. a

We have found that the addition of certain chemical substances which arederived by the substitution of one or more of the hydrogen atoms ofammonia by other groups or radicles, to the lime, or other unhairingsolution, has a very marked effect in reducing the amount of timerequired for the unwhich comprlses sub]ect1ng it to the act1onhairing'operation and no undesirable effects upon either skin or hairare produced.

Our invention refers to and includes all compounds containing primary,secondary or tertiary amino groups and whether of alkvl or of arylderivation.

We have found the primary amines known as ethyl amine and methyl amineto be most effective but the di and tri amines are also useful, as wellas those compounds known as amides. such as, for example, acetamide(CILCONHQ The amount of amine compound necessary to be added to the lime(or other) solution varies with the type of skin to be unhaired and withits chemical condition or composition. In the caseof a well cured skinof va steer we have found that Whereas one hundred and twenty hoursimmersion of the skin in a bath of saturated lime solution, at twentydegrees centigrade, are required for proper unhairing and conditioning,this time may be reduced to from forty-eight to seventy-two hours ifeither ethyl or methyl amine is added to the lime solution, in theproportion of one pound of the amine to'each one hundred pounds of limesolution. The necessary amount of other amine compounds va- .ries withtheir chemical composition.

We claim:

1. The process of dehairing a cured skin .of a steer which comprisessubjecting it to the action of a bath containing saturated lime solution"to which-has been added about one percent of an amine of thecomposition OnHantmJNH-ih 2. The process of dehairing animal skin whichcomprises subjecting it to the action of a bath containing saturatedlime solution to which has been added the proper amount .of an amine ofthe composition until the skins hair may bereadily removed. 3. Theprocess of dehairing an animal skin hydroxide and-primary alkyl aminesuntil the skins hair may be readily removed.

4. The process of dehairing an animal'skin which comprises subjecting itto the action of a bath containing saturated lime solution to which hasbeen added about one-percent of methyl amine until the skins hair may bereadily removed;

5. The process of dehairing animal skin consisting of submersing it in abath containing limesolution and one element of the group comprisingmethyl amine, ethyl amine and a mixture'of methyl amine and ethyl amineuntil the skins hair may be readily removed. 6. The process ofconditioning animal skin of a bath containing alkaline solution to whichhas been added an amine of the comosition in such quantity as to producea bath for I I (2n+2)-= Ha)z until'the skin is conditioned for tanning.

8. A bath for dehairing animal skin containing saturated lime solutionto which has been added about one percent of an amine of the composition9. A bath for dehairing animal skin containing saturated lime solutionto which has beenadded. about one per cent of methyl amme.

signatures.

GEORGE DUNLAP MoLAUGI-ILIN. GEORGE EDMUND ROCKWELL. FREDERICK OFLAHERTY.

J OHN' HENRY, HIGHBERGER'.

which comprises subjecting it to the action of-a'bath containing asolution of calcium- In testimony whereof we hereto affix our I

